When Iori Kitahara heads off to university, he chooses to move into his uncle's dive store in Izu, known as Grand Blue. Iori is eager to begin his life as a student, surrounded by the roar of the waves, the intense sun, and his cousin who lives with him. However, Iori meets a group of tough guys with a passion for rock-paper-scissors strip games, and joins the university's diving club, Peek-a-Boo.